(a) Deletion of the H3-H4 tails results in partial inhibition of compaction. Electrophoretic analysis in native 0.9% agarose of the compaction state of 202bp × 61 nucleosome arrays fully reconstituted with histone octamers containing combinations of N-terminal tail deletions as indicated above the lanes: Chicken erythrocyte (CE); wild type recombinant (WT); H3-H4 tailless (gH3gH4); H2A-H2B-tailless (gH2AgH2B); and completely tailless (gAll) histone octamers. The presence of the linker histone H5 is indicated (+). Arrays were folded in 1.6mM Mg2Cl and 20mM TEA pH7.4 and analysed in both the unfixed (−) or fixed state (+). Fixation was by 0.1% (v/v) glutaraldehyde. The migration in the gel reflects the compaction state of the nucleosome array: the faster migration the more compact the fibre.
(b) Deletion of the H4 tail has the most crucial effect on compaction. Electrophoretic analysis in native 0.9% agarose of the compaction state of 202bp × 61 nucleosome arrays fully reconstituted with different histone octamers as indicated above the lanes: tailless H3 (gH3) and tailless H4 (gH4). The presence of the linker histone H5 is indicated (+). The nucleosome arrays were reconstituted, folded and fixed as in (a).